1. Field of the Invention
The present invention relates to an idle-to-active state shift or handover, and more particularly, to an idle-to-active state shift or handover in a carrier aggregation environment.
2. Description of the Related Art
A carrier aggregation environment may be a technology of enhancing a data transmission efficiency by merging a plurality of carrier components.
FIG. 1A is a diagram to describe a frequency band in a carrier aggregation environment according to a conventional art.
It is assumed that a communication system of the carrier aggregation environment uses a first frequency band 110 and a third frequency band 130, and a second frequency band 120 is used by another communication apparatus.
The first frequency band 110 and the third frequency band 130 used by the communication system of the carrier aggregation environment may include a plurality of carrier components. For example, the first frequency band 110 may include carrier components 111, 112, 113, and 114, and the third frequency band 130 may include carrier components 131, 132, 133, and 134. The communication system may select at least one carrier component and transmit data using the selected at least one carrier component.
The communication system may select neighboring carrier components, for example, the carrier components 111 and 112, or may select separate carrier components, for example, the carrier components 111 and 113.
In addition, the communication system may select carrier components of separate frequency bands. For example, the communication system may select a carrier component positioned in the first frequency band 110, and a carrier component positioned in the third frequency 130.
The communication system may merge the selected carrier components, and may transmit data using the merged carrier component.
FIG. 1B is a diagram illustrating a relationship among a terminal 140 and a base station 150 included in a communication system, and each carrier component.
Referring to FIG. 1B, the terminal 140 may select two carrier components (CC1 and CC2) 141 and 142. The base station 150 may select four carrier components (CCa, CCb, CCc, and CCd) 151, 152, 153, and 154. When the terminal 140 and the base station 150 select the same carrier component, data may be transmitted between the terminal 140 and the base station 150.
For example, when the base station 150 selects fourth carrier components 111, 112, 113, and 114, the carrier components (CCa, CCb, CCc, and CCd) 151, 152, 153, and 154 usable by the base station 150 may correspond to the carrier components 111, 112, 113, and 114, respectively. In this case, when one of the carrier components (CC1 and CC2) 141 and 142 usable by the terminal 140 corresponds to one of the carrier components 111, 112, 113, and 114, data may be transmitted between the terminal 140 and the base station 150.
The conventional mobile communication system may perform an idle-to-active state shift or handover based on only a single carrier component.
FIG. 2A is a flowchart illustrating a conventional idle-to-active state procedure.
When an uplink packet occurs in a terminal 210, or when the terminal 210 receives a paging message from a base station 220 in operation S230, the terminal 210 may start shifting from an idle state to an active state.
In operation S240, the terminal 210 may perform a Radio Resource Control (RRC) connection establishment procedure through a random access procedure.
In operation S250, the terminal 210 may receive an RRC reconfiguration request message from the base station 220. The RRC reconfiguration message may include information used for the terminal 210 to establish a radio bearer.
In operation S260, the terminal 210 may establish the radio bearer, and may transmit an RRC reconfiguration complete message to the base station 220.
FIG. 2B is a flowchart illustrating a conventional handover procedure.
In operation S291, when a base station 280 determines to perform a handover, the base station 280 may transmit a handover start message to a terminal. The handover start message may be transmitted in a form of an RRC reconfiguration request message.
In operation S292, the terminal 270 may perform a handover according to the handover start message, and may transmit an RRC reconfiguration complete message to the base station 280.
In the conventional art, the state shift and the handover may be performed based on only a single carrier component.